Aluminum matrix composite wires, cables, and method

Details Aluminum matrix composite wires, cables, and method Aluminum matrix composite wires, cables, and method

2002-11-19

2004-02-17

Zimmerman, John J. (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Having magnetic properties, or preformed fiber orientation...

C428S614000, C428S539500

Reexamination Certificate

active

06692842

ABSTRACT:

FIELD OF THE INVENTION
The present invention pertains to composite wires reinforced with substantially continuous ceramic oxide fibers within an aluminum matrix and cables incorporating such wires.
BACKGROUND OF THE INVENTION
Metal matrix composites (MMC's) have long been recognized as promising materials due to their combination of high strength and stiffness combined with low weight. MMC's typically include a metal matrix reinforced with fibers. In selection of the fiber, it is widely acknowledged that one desires reinforcement fibers possessing high strength, a high elastic modulus, and a low coefficient of thermal expansion.
The use of metal matrix composites in the form of wires as a reinforcing member in bare overhead power transmission cables is of particular interest. The need for new materials in such cables is driven by the need to increase the power transfer capacity of existing transmission infrastructure due to load growth and changes in power flow due to deregulation. Desired performance requirements for such new materials include corrosion resistance, environmental endurance (e.g., UV and moisture), retention of strength at elevated temperatures, and creep resistance.
Important properties for performance are elastic modulus, density, coefficient of thermal expansion, conductivity, and strength. These properties are typically governed by the choice and purity of constituents (i.e. material of the metal matrix and the fiber content) in combination with the fiber volume fraction. Of these properties, emphasis has been placed on the development of wires made from fibers with high tensile strength and stiffness. The focus on producing materials of high strength is driven in part by the assumption that ii, order for the composite to compete economically with conventional materials such a steel, its strength should be as high as possible. For example, in Ozawa et al., “Mechanical Properties of Composite Conductors using SiC Fiber Resinforced Aluminum Composite Wires,”
The Electricity Society National Symposium,
1996, which discloses an aluminum wire reinforccd with high strength fiber marketed under the trade designation “NICALON,” the need for MMC wires of “high strength” for use in overhead power transmission cables is described.
There is still a need for composite materials that have suitable properties for use in a wide variety of cables, particularly overhead power transmission cables.
SUMMARY OF THE INVENTION
The present invention relates to substantially continuous fiber aluminum matrix composites. Embodiments of the present invention pertain to aluminum matrix composite articles, preferably elongated metal composite articles such as wires, tapes, etc. Such articles preferably include a plurality of substantially continuous, longitudinally positioned fibers contained within a matrix that includes aluminum (e.g., high purity aluminum or alloys thereof). Preferably, the matrix of the wire includes at least 99.95 percent by weight aluminum, based on the total weight of the matrix.
The aluminum matrix composites of the present invention are formed into wires exhibiting desirable strength-to-weight and thermal expansion characteristics, high electrical conductivity, and low modulus. Such wires are well-suited for use as core materials in power transmission cables, as they provide electrical and physical characteristics which offer improvements over power transmission cables known in the prior art.
The materials of the present invention are advantageous for wires and cables because they provide less sag when heated due to the low coefficient of thermal expansion. Additionally, compared with steel wires or composite wires reinforced with high modulus materials, the wires of the present invention are capable of reducing the tension on supporting towers when the cables are exposed to high mechanical loads (such as combined ice and wind load) due to their low modulus.
In one embodiment, the present invention provides an aluminum matrix composite article that includes a plurality of fibers in a matrix including aluminum. In this embodiment, the fibers include, on a theoretical oxide basis, Al
2
O
3
in a range of about 35 weight percent to about 75 weight percent, SiO
2
in a range of greater than zero weight percent to less than about 50 weight percent, and B
2
O
3
in a range of greater than about 5 weight percent, based on the total metal oxide content of the respective fiber. In this embodiment the wire has a nonlinear coefficient of thermal expansion over a temperature of −75° C. to 500° C., a modulus of no greater than about 105 GPa (15 Msi), and an average tensile strength of at least about 350 MPa (50 ksi).
In another embodiment, the present invention provides an aluminum matrix composite wire that includes a plurality of substantially continuous, longitudinally positioned fibers in a matrix including aluminum. In this embodiment, the fibers include, on a theoretical oxide basis, Al
2
O
3
in a range of about 35 weight percent to about 75 weight percent, SiO
2
in a range of greater than zero weight percent to less than about 50 weight percent, and B
2
O
3
in a range of greater than about 5 weight percent, based on the total metal oxide content of the respective fiber. In this embodiment the wire has a nonlinear coefficient of thermal expansion over a temperature of −75° C. to 500° C., a modulus of no greater than about 105 GPa (15 Msi), and an average tensile strength of at least about 350 MPa (50 ksi).
In another embodiment, the present invention provides a method for making an aluminum matrix composite wire that includes a plurality of substantially continuous, longitudinally positioned fibers in a matrix that includes aluminum. The method includes: providing a contained volume of molten matrix material; immersing a plurality of substantially continuous fibers into the contained volume of molten matrix material wherein the fibers comprise, on a theoretical oxide basis, Al
2
O
3
in a range of about 35 weight percent to about 75 weight percent, SiO
2
in a range of greater than zero weight percent to less than about 50 weight percent, and B
2
O
3
in a range of greater than about 5 weight percent, based on the total metal oxide content of the respective fiber; imparting ultrasonic energy to cause vibration of at least a portion of the contained volume of molten matrix material to permit at least a portion of the molten matrix material to infiltrate into and wet the plurality of fibers such that an infiltrated, wetted plurality of fibers is provided; and withdrawing the infiltrated, wetted plurality of fibers from the contained volume of molten matrix material under conditions which permit the molten matrix material to solidify to provide an aluminum matrix composite wire comprising a plurality of the fibers, wherein the fibers are substantially continuous, longitudinally positioned in a matrix including aluminum, and wherein the wire has a nonlinear coefficient of thermal expansion over a temperature of −75° C. to 500° C., a modulus of no greater than about 105 GPa, and an average tensile strength of at least about 350 MPa.
In another embodiment, the present invention provides a cable that includes at least one aluminum matrix composite wire that includes a plurality of substantially continuous, longitudinally positioned fibers in a matrix including aluminum. In this embodiment, the fibers include, on a theoretical oxide basis, Al
2
O
3
in a range of about 35 weight percent to about 75 weight percent, SiO
2
in a range of greater than zero weight percent to less than about 50 weight percent, and B
2
O
3
in an amount of greater than about weight 5 percent, based on the total metal oxide content of the respective fiber. Furthermore, in this embodiment, the wire has a nonlinear coefficient of thermal expansion over a temperature of −75° C. to 500° C., a modulus of no greater than about 105 GPa, and an average tensile strength of at least about 350 MPa.
In yet another embodiment, the present invention provides an aluminum matri

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